Hello Christine,
Thank you for your question. I think you need to go to the billing area and click change subscription and choose the annual one.
If it doesn't work, you can cancel your monthly subscription and wait until you will lose full access to the website (if you cancel in the middle of the month, you will still be able to learn with Repeto for 15 days).
And then, please buy an annual subscription.
I hope this will help, please let me know if you need further support.
By the way... would you like to take part in an online Polish class? It is free for Repeto subscribers. I run it every Wednesday at 4pm UK time. If so, please email me info[at]repeto.org. Thank you.